How the Earth Was Made: Asteroids. (2013). The History Channel website. Retrieved 3:32, May 23, 2013, from http://www.history.com/shows/how-the-earth-was-made/videos/playlists/.
How the Earth Was Made: Asteroids. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/shows/how-the-earth-was-made/videos/playlists/ [Accessed 23 May 2013].
“How the Earth Was Made: Asteroids.” 2013. The History Channel website. May 23 2013, 3:32 http://www.history.com/shows/how-the-earth-was-made/videos/playlists/.
“How the Earth Was Made: Asteroids,” The History Channel website, 2013, http://www.history.com/shows/how-the-earth-was-made/videos/playlists/ [accessed May 23, 2013].
“How the Earth Was Made: Asteroids,” The History Channel website, http://www.history.com/shows/how-the-earth-was-made/videos/playlists/ (accessed May 23, 2013).
How the Earth Was Made: Asteroids [Internet]. The History Channel website; 2013 [cited 2013 May 23] Available from: http://www.history.com/shows/how-the-earth-was-made/videos/playlists/.
How the Earth Was Made: Asteroids, http://www.history.com/shows/how-the-earth-was-made/videos/playlists/ (last visited May 23, 2013).
How the Earth Was Made: Asteroids. The History Channel website. 2013. Available at: http://www.history.com/shows/how-the-earth-was-made/videos/playlists/. Accessed May 23, 2013.